It's impossible to know whether that riddle would survive offensive line scrutiny, since only rookies are summoned to deliver daily words of wisdom to open meetings in the Vikings' longest-tenured position room.

And a joke. Dirty or clean. Preferably dirty. Banned are knock-knock gags or rim shots.

"I bought a joke book the other day," rookie guard David Yankey said this week. "I always have a couple with me in my locker to have one ready to go. You really want to find a good joke. If not, they're going to boo you."

Offensive linemen typically toil in the shadows, but the spotlight this season is on Minnesota's front five as the team incorporates its conventional ground game with a diversified passing attack under new coordinator Norv Turner.

They opened holes for Adrian Peterson to gain 2,097 yards in 2012 but were inconsistent protecting a Lazy Susan of quarterbacks last season. Now the job is more demanding.

Deeper drops to support an aggressive downfield passing game, and longer check-downs, require stronger and more mobile protection schemes to maintain a clean pocket.

"We're certainly taking longer shots down the field than we have before," said left guard Charlie Johnson. "We know that it's really about holding on that extra second to get the ball away."

Turns out the best teachers for center John Sullivan, guards Johnson and Brandon Fusco, and tackles Matt Kalil and Phil Loadholt, is Minnesota's fluid defense and the new formations and blitzes showcased this preseason.

The Vikings' defensive line has been overhauled. Gone are stalwarts Jared Allen rushing off the edge and run stuffer Kevin Williams. They have been replaced by Everson Griffen, who has been trouble to contain, and a slimmed-down Sharrif Floyd, the second-year tackle trying to reboot after a disappointing rookie season.

And then there is rookie linebacker Anthony Barr, a wild card who can create another mismatch as a pass rusher.

"We have a great resource in our defense in that they bring every blitz known to mankind," said offensive line coach Jeff Davidson. "Every day we feel comfortable with it, there's a little bit of a curveball and we have to respond to that. So we're constantly evolving with our protection schemes. We're learning something new each day."

Turner has said the most demanding positions are on the offensive line, which has to prepare for more exotic blitzes and pressure as teams work to expand the vertical passing game.

He spent hours scrutinizing the Vikings' returning starters before determining that this unit could adjust to the nuances of his scheme and prepare for tougher tasks.

"When you watch this offensive line, and they are playing at their best, at a high level, then, yes, they are good enough for us to go have success," Turner said. "We are trying to get them ready to win."

Kalil is under scrutiny. He and Johnson struggled at times in 2013 to protect the quarterback's blind side. Healthy after offseason knee surgery, Kalil knows he needs to perform better than his sophomore slump, which followed a Pro Bowl rookie season in 2012.

"It's getting back to two years ago, that continuity and dominating offensive line," Kalil said. "I think we're going to have a great year."

It starts at center with Sullivan, the dean of the group responsible for communicating the protection at the line. He also works most closely with Davidson to resolve communication breakdowns and keep the 10 reserves engaged.

"Sully's definitely the dominant voice in there as the veteran," Kalil said. "We'll joke sometimes and say it's the Jeff Davidson-Sully meetings because it's just them going over calls and we're just listening."

Levity certainly helps.

For years, rookie offensive linemen have been required to tell a joke every day. The team added riddles this season.

Yankey, a physical guard drafted in the fifth round out of Stanford, has told about 10 jokes and five riddles after Googling several.

"I demand an answer but I ask no question," was the one that spared him boos and rotten tomatoes.

Yankey marvels at the unspoken communication among the starting five and their ability to cover for one another. Three straight seasons under Davidson's direction has made continuity the buzzword.

Sullivan said that manifested itself during last week's preseason victory over the Arizona Cardinals.

On tight end Kyle Rudolph's 51-yard touchdown reception, the Cardinals stunted the nose tackle and blitzed the middle linebacker. Sullivan and Fusco reacted quickly, sealing off the pressure and allowing Matt Cassel to set his feet and deliver a strike.

"Fusco and I hadn't practiced picking that up because we hadn't seen it on tape," Sullivan said. "Because we're used to playing with each other, we passed it off seamlessly. Obviously, (if) you protect the quarterback in that situation, good things happen."